Improvement in treating straw for paper-pulp



UNITED STATES PATENT OFFICE.

HARRISON B. MEEOH, OF FORT EDWARD, NEW YORK.

IMPROVEMENT lN TREATING STRAW FOR PAPER-PULP.

Specification forming part of Letters Patent No. 50,835, dated November7, 1865.

To all whom "it may concern:

Be it known that I, HARRISON B. MEEoH, of Fort Edward, in the county ofWashington and State of New York, have invented a new and improvedprocess for treating straw for the purpose of preparing the same to beconverted into pulp for the manufacture of white paper for writing,printing, and other purposes for which white paper is used; and I herebydeclare that the following is an exact description of said process.

The character and quality of the pulp made from straw depends entirelyupon the mode of treatment by which it is produced. 1f the alkalineliquor used in the reduction of the straw be of too high a degree ofstrength, there will benotonlyawaste ofthea1kali,but thefiber will be ina measure reduced to a pasty condition and will waste largely during theafter process of washing the stock; besides, the quality of the stockwill be injured by being made short, and thereby injuring the strengthof the paper to be manufactured therefrom.

Another difficulty has attended the treatment of straw preparatory tothe manufacture of pulp therefrom, and that is there has been too muchagitation during the period of boiling or cooking the straw.

The usual course of treatment by those using rotary boilers has been tocommence the rotation of them as soon as the heat began to be applied,and to continue their rotation until the boiling or cooking was finishedand the mass treated was ready to be discharged. The effect of thiscontinued agitation was to separate the portions of straw first actedupon from the stock or stem of the straw and expose such finer portionthus separated to the further action of the alkali, thereby reducing itto a semi-fluid or pasty condition. My experience has been that the lessagitation there is vof the straw during the period of its treatment inalkali without permitting it to burn the better. There is another evilconsequence attending the too early rotation of the boiler Whileintroducing the liquor and raising the temperature. Ifthe boiler isrotated while the contents are unequally saturated with the alkalineliquor, the consequence will be that the contents of the boiler willbeagglomerated together in uneven and unequal mass, making it impossibleafterward to treat the mass evenly. For that reason I have found thatthe better way was to allow the rotary to remain at rest while chargingthe same with the straw and the necessary amount of liquor. By thismeans the mass in the boiler was undisturbed until the liquor was fullyin, and when the rotation afterward commenced the action within therotary would be more even and uniform. I have thus found it to be thebest practice not to commence rotating the boiler until I had fullycharged it with the straw and liquor, and had let the steam into and putthe fire under the same.

My only object in rotating the boiler during the treatment of the strawis to prevent burning the material within the rotary. For that reason assoon as a temperature indicated by an internal pressure of one hundredpounds to the square inch within the boiler is attained I stop the fireand cease rotating the boiler. The principle is this: There should be aslittle agitation of the straw as possible after the boiling hasprogressed far enough to begin to separate the fine particles of strawfrom the stock. This point is reached as soon as the one hundred poundspressure is obtained. Then the boiler should rest. the fire he stopped,and it should be permitted to stand and cook for aboutthree hourslonger, when it will be found that the stock is well prepared forwashing. I also find it advisable to use a much weaker liquor forboiling than has been heretofore used. A liquor marking from 3 to 5 ofstrength Bapm hasformerlybeen used. The result was that the fiber wasmuch shortened and injured thereby. Much of the stock was therebyconverted to a paste and washed away in the after treatment. I havefound it better to use a much weaker solution of caustic alkali, markingin strength from 1 to 2 Bauni, and never exceeding 2 strength. I havealso found that it is much better to increase the quantity of liquor,even when byso doing the strength of the boiling liquor is'reduced. ThusI use about eighteen hundred gallons of the weaker liquor where othersuse about fourteen hundred gallons-that is, were I to take their liquorat fourteen hundred gallons to twentytwo hundred pounds of straw, Ishould find it a better practice to add from four hundred to six hundredgallons of clear soft water, thereby redueing the strength of theirboiling-liquor in that proportion. The reason for this is, first, byincreasing the quantity of the boilingliquor the straw being treated ismore completely immersed continually in the boiling liquor; second, thestrength of the liquor thus diluted does not injure the fibers of thestock being treated, and the result is 1 get a more uniform, longer, andbetter fiber.

My method of preparing my boilingliquor is as follows: It is composed ofwater, soda ash, and lime, and also grease or other like alkaline andoleaginous substance. In preparing such liquor I use three iron pans,hold ing one thousand gallons each, with agitators to mix the soda-ashand lime with the water. I also use a reservoir holding about twothousand gallons. I then take five hundred and fifty pounds of soda-ash,dissolve it in a pan of water holding one thousand gallons, to which Iadd about three hundred and eighty-five pounds of unslaked lime, orsufficient lime to combine with and properly caustify the sodaash, whichwill be according to the strength of the lime. By means of siphon I drawabout one-third of this liquor into the reservoir. I then add water tothat in the pan, agitate it, let it settle, and draw off, as before,into the reservoir. I proceed in this way four times, or until I have inmy reservoir about eighteen hundred gallons of liquor testing at from 1to 2 Baum. lVhat remains in the pan I use in the preparation of theliquor for the next boiling. ()f the liquor thus prepared I use aboutseventy gallons to the one hundred pounds of straw prepared and packedin the boiler, as follows: In addition to this liquor, I take aboutsixteen pounds of grease or other oily substance, and twelve pounds ofsoda-ash or potash, and boil them in sixty gallons of water by steamuntil a soapy solution is produced.

I prepare my straw thus I cut it intolengths of about two inches, passit through a fanningmill to separate any grain there may be in it. Iremove all weeds and sticks, then pass it through heavy iron rollers forthe purpose of crushing the knots and straw and increasing the surfaceexposed to the action of the alkali. I then charge my rotary with it,packing itin as closely as two men can do by stamping it in, for I findthe more compactI can make the straw within the boiler the more perfectis the action of the alkaline solution upon it. My boiler is six feet indiameter and twenty-two feet in length, and I thus put into it abouttwenty-eight hundred pounds of straw to a boiling. Having thus chargedmy boiler with straw, I then pour upon the straw Within the boiler thesoapy solution prepared as about hot, together with a weak alkalinesolution, prepared as above described, taking care that the boiler shallremain stationary while filling in the entire quantity of liquor, forreasons already stated. After my boiler is thus full, charged with strawand the proper amount of boiling-liquor and soapy solution, I commencerotating it and letting in steam from the adjoining boiler in the methodwell known to the art, and, also, I put a fire under the rotating boilerand raise the temperature thereby to such a degree as is indicated by aninternal pressure of one hundred pounds to the square inch within theboiler. As soon as this degree of temperature is indicated I stop therotation of the boiler and remove the fire from beneath the same andpermit itthus to remain for from two to three hours, when the straw isproperly cooked and prepared for washing and treating in the manner Wellknown to the art and trade of paper-making.

By this particular method of treatment I obtain a superior quality ofstockfor the manufacture of paper-pulp.- The fiber is freed from foreignsubstances, is long, strong, and little or none of it is reduced to apaste or a state by which it is wasted in the after-washing process.

Having thus fully described my improvement, what I claim as myinvention, and for which I desire to secure Letters Patent, is-- 1. Myabove-described method of treating straw or other material preparatoryfor making paper-pulp by so charging it into the boiler, letting intoand onto it the liquor and solutions, applying the steam and fire heat,rotating the boiler, and letting the same remain at rest,in the mannersubstantially and for the purpose ZLbOW-L, described.

2. The use of a weak alkaline liquor, not to exceed 2 of strength,(Baum,) in the treatment of straw under pressure, in the mannersubstantially and for the purpose above described.

3. The combination of the use of such weak alkaline liquor with mymethod of treating straw, as set out in my first claim herein, in themanner substantially and for the purpose above described.

HARRISON B. MEEGEI. Witnesses:

ASAHEL WING,

A. O. HOSSMAN.

